Current state of the art solutions for coupling light to and from a waveguide of a photonic integrated circuit (PIC) typically require precise alignment and/or fabrication. In silicon on insulator (SOI) PIC platforms, it is possible for the mode of a waveguide to have submicron dimensions. Edge-to-edge coupling of modes between these PICs would require aligning sub-micron optical modes or would require utilizing spot-size converters to expand and contract these modes for coupling. Surface-normal solutions for coupling sub-micron sized modes between these PICs could be accomplished by expanding and redirecting the beams with gratings or by redirecting the beams with mirrors. Both methods require additional fabrication steps. Fabrication of gratings requires high-resolution lithography, and results in sub-optimal coupling efficiency. Mirrors used for coupling will not expand the mode size, leading to a submicron alignment requirement.
Descriptions of certain details and implementations follow, including a description of the figures, which may depict some or all of the embodiments described below, as well as discussing other potential embodiments or implementations of the inventive concepts presented herein. An overview of embodiments of the invention is provided below, followed by a more detailed description with reference to the drawings.